VIENNA, Austria — The International Atomic Energy Agency on Thursday reported significant cooperation from Iran with its nuclear probe and noted that Tehran had slowed uranium enrichment — assessments that could hamper U.S. hopes for new U.N. sanctions.

GEORGE JAHN

VIENNA, Austria — The International Atomic Energy Agency on Thursday reported significant cooperation from Iran with its nuclear probe and noted that Tehran had slowed uranium enrichment — assessments that could hamper U.S. hopes for new U.N. sanctions.

Iran said the report proved it was the target of unfair U.S. attacks. But Washington and its allies said it did not change the need for more U.N. Security Council penalties.

IAEA Deputy Director-General Olli Heinonen highlighted the importance of Tehran's cooperation, noting that its past stonewalling had triggered Security Council sanctions in the first place. But he cautioned that Iran still needed to prove it would abide by its commitments.

The report said a recently agreed Iran-IAEA cooperation plan was a "significant step forward" but the U.S. played down suggestions of progress.

"I don't see anything, at this point, in this report, that changes the basic facts," State Department spokesman Tom Casey said in Washington. "The international community is going to continue to ratchet up the pressure."

Noting the continuation of the enrichment program — which can make both nuclear fuel and fissile warhead material — Casey urged Tehran to "serve the real needs of their people instead of trying to pursue a nuclear weapon."

France was even more direct. Foreign Ministry spokeswoman Pascale Andreani declared that without an enrichment freeze, Paris will "pursue ... looking into a third sanctions resolution."

Drawn up by IAEA chief Mohamed ElBaradei, much of the confidential report obtained by The Associated Press focused on the already publicized Iran-IAEA cooperation plan, restating progress in some areas and time frames for Iran to respond to additional questions.

In that plan, Iran agreed to answer most questions from agency experts by November.

If that and all other deadlines are met and Iran provides all the information sought, the agency should be able to close the file on its more than four-year investigation of Tehran's nuclear activities by year's end, a senior U.N. official said.

He and other U.N. officials — all speaking on condition of anonymity because they were not authorized to comment to media — declined to speculate on whether a clean bill that banishes suspicions about Iran's former nuclear programs and experiments would be enough to derail the threat of new U.N. sanctions.

Besides refusal to halt its uranium enrichment program, Tehran also continues to defy the Security Council by building a plutonium-producing reactor — another pathway to nuclear arms.

Repeating the findings of the Iran-IAEA cooperation plan, the report — to be considered by the 35-nation IAEA board at a meeting starting Sept. 10 — said the agency felt that information provided by Iran on past small-scale plutonium experiments had resolved agency concerns about the issue.

In Tehran, the official Islamic Republic News Agency cited senior nuclear official Mohammad Saeedi as saying that conclusion "ended all the baseless U.S. accusations against Iran over reprocessing plutonium."

The agency report also noted cooperation on other issues, while specifying that Tehran still needed to satisfy the agency's curiosity about its enrichment technology and traces of highly enriched uranium at a facility linked to the military.

The report also said Iran agreed to study documentation from the agency on the "Green Salt Project" — a plan that the U.S. alleges links diverse components of a nuclear weapons program, including uranium enrichment, high explosives testing and a missile re-entry vehicle.

Diplomats told the AP last year that the agency was made aware of the alleged program by U.S. intelligence. One of the U.N. officials suggested the IAEA might share its confidential documents — possibly including secret U.S. information — with Iran in its investigation of the "Green Salt Project," but declined to offer details.

While Iran continued to expand its uranium enrichment program, the report showed it was doing so much more slowly than expected, and had produced only negligible amounts of nuclear fuel, far below the level usable for nuclear warheads.

One U.N. official also noted that construction of a plutonium-producing reactor in the city of Arak had slowed in recent months.

He said "design difficulties, getting equipment, materials and components, and fuel technology, plus perhaps some political considerations," could be causing the delay.

The allusion to "political considerations" appeared to be linked to reports that Iranian officials might be considering stopping construction of the Arak reactor in another sign of goodwill calculated to blunt the threat of new U.N. sanctions.

Citing unidentified Iranian sources, Jane's Defense Weekly earlier this week said some members of Iran's Supreme National Security Council were pushing for such a move.